The National Park Service Inventory & Monitoring Division (IMD) consists of 32 networks that gather and analyze inventory and monitoring data, and communicate key information on park resources. The monitoring data helps park managers understand how the natural resources are changing over time, enabling them to make science-based management decisions.
Inventory and Monitoring Division (U.S. National Park Service). (n.d.). Retrieved December 13, 2025, from https://www.nps.gov/im/index.htm
The Northern Colorado Plateau Network (NCPN) conducts monitoring for 16 different park units. Upland Vegetation and Soils is considered a high monitoring priority since most of land on the Colorado Plateau is upland ecosystems. Upland areas include rock outcrops, shrublands, grasslands, woodlands, forests, badlands, and subalpine meadows. Plant communities, exotic invasive species, biological soil crusts, soil stability, and hydrologic function are monitored in uplands ecosystems.
Understanding how vegetation cover changes over time helps park managers to detect shifts in plant communities, identify at-risk areas, and make informed management decisions. This analysis quantifies vegetation cover trends at Arches National Park as an example of how upland vegetation monitoring can provide information for resource management and conservation efforts.
Witwicki D, Thomas H, Weissinger R, Wight A, Topp S, Garman SL, Miller ME. 2017. Upland vegetation and soils monitoring protocol for park units in the Northern Colorado Plateau Network: version 1.07. Natural Resource Report. NPS/NCPN/NRR—2017/1570. National Park Service. Fort Collins, Colorado https://irma.nps.gov/DataStore/Reference/Profile/2248124
Upland Vegetation and Soils (U.S. National Park Service). (n.d.). Retrieved December 13, 2025, from https://www.nps.gov/im/ncpn/uplands.htm
Arches National Park is located north of Moab in Southeast Utah and is part of NCPN. Elevation in the park ranges from about 4,000 feet in the canyons to 5,200 feet on the rims. With an arid climate, the summers are hot and dry, and the winters are cool to cold. Average annual precipitation is about 8 inches, and temperatures can reach extremes, from -16F to 112F. Most of the park is covered by exposed bedrock, weakly developed soils, and sand dunes. The most common vegetation type in the park is desert shurblands, but woodlands and sparse woodlands are also common.
Biophysical Description of Arches National Park (U.S. National Park Service). (n.d.). Retrieved December 13, 2025, from https://www.nps.gov/im/ncpn/bpd-arch.htm
Natural resources monitoring at Arches National Park (U.S. National Park Service). (n.d.). Retrieved December 13, 2025, from https://www.nps.gov/im/ncpn/arch.htm
Uplands monitoring began in Arches National Park in 2010 to address the management issue of social trailing, and approximately 2,500 hectares are monitored. The sampling unit is a plot and consists of three parallel, 50-meter transects that are spaced 25 meters apart. To increase the overall sample size, a rotating panel design is used where plots are sampled 1-2 years in a row with 3-6 years of rest.
The point-intercept method is used for estimating vegetation and soil surface cover for grassland/shrubland vegetation types. Vegetation and ground cover attributes are recorded at 0.5-meter intervals. A laser is used at each point, and any vegetation, dead or alive, that the laser intercepts is recorded. Additionally, vegetation at any height is recorded.
The Upland Vegetation and Soils Monitoring Protocol, provides in-depth details about the sampling design.
Sources: Hobbs A, Wight A, Livensperger C, Witwicki D, Thomas H, Brehm JR, Miller ME, Weissinger R, Topp S, Garman SL. 2024. Upland Vegetation and Soils Monitoring for the Northern Colorado Plateau Network: 2009-2023 - Data Package. National Park Service. Fort Collins CO https://doi.org/10.57830/2305079
Witwicki D, Thomas H, Weissinger R, Wight A, Topp S, Garman SL, Miller ME. 2017. Upland vegetation and soils monitoring protocol for park units in the Northern Colorado Plateau Network: version 1.07. Natural Resource Report. NPS/NCPN/NRR—2017/1570. National Park Service. Fort Collins, Colorado https://irma.nps.gov/DataStore/Reference/Profile/2248124
Source: Veg Records
1,969
Plots
84
Species
106
I downloaded the NCPN point-intercept CSV, read it into R, filtered for only Arches National Park and live vegetation records, then calculated percent cover by species to the plot level.
Since there are 84 plots, I wanted to explore the data to find a meaningful but efficient way to show vegetation cover changes over time or identify particular plots to focus on. First, I calculated percent change for each species using min and max values, regardless of year. Next, I calculated percent change for each species from the first to last survey year. For both, I reviewed species with 10 percent change or greater and identified select plots and species to focus on (see tables to the right).
To visualize the vegetation cover change, I converted cover from percentage to area, summed the cover area by species and year, and then calculated the percent area (species cover area / total area sampled * 100).
Data, scripts, and outputs are on GitHub.
The plot-level charts focus on species with large changes in cover over time that I selected based on their frequency in the Species Change and Species Trend tables. The park-level charts show changes in vegetation cover by area across all plots. The species list contains select data from the species lookup table for the species shown in the charts.
Arches National Park Vegetation Cover Per Plot
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Arches National Park Total Vegetation Cover (Area)
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Without knowledge of management actions or other events at the park, and with no location data, I can only speculate as to why vegetation cover changed over time at the selected plots.
Between 2015 and 2022, the cover of an invasive annual grass (ERTR13) increased by over 15 percent. At Plot 91, between 2015 and 2022, the cover of an invasive annual grass (BRTE) increased by over 20 percent. This could be due to some type of disturbance, and I initially thought fire because of the low vegetation cover at Plot 91 in 2021, but I did not find any reports of fires in the park in 2020 or 2021.
The cover of an invasive annual (SATR12), increases in 2022 at Plot 101, and then was not even recorded in 2023. This could be due to an invasive species treatment.
Although I cannot explain why the changes in vegetation cover occurred, this analysis demonstrates how vegetation cover data are helpful for park managers to detect shifts in plant communities. For example, we can see an increase in invasive annual grasses, which could prompt park managers to implement invasive species treatments.
Looking at low percentages of Indian Ricegrass cover in grasslands, it appears that this native perennial grass has been outcompeted by invasive annual grasses.
